Aromatase inhibitors may slow growth of lung cancer in women

A few years ago researchers discovered that, much like breast tumors, some lung tumors also thrive on estrogen.
Now researchers at the Howard Hughes Medical Institute ( HHMI ) have managed to stop the growth of human lung cancer cells in mice with a class of breast cancer drugs called aromatase inhibitors.

The studies are reported in the journal Cancer Research.

The findings suggest a new way to treat lung cancer in women  a group whose death rate from the disease is surging.

To see if they could block this growth, the team started with the enzyme aromatase. It presented a natural target because aromatase converts testosterone into estradiol, a potent form of estrogen also used in hormone replacement therapy.
In addition, drugs that inhibit aromatase have already made it to market as new treatments for breast cancer.

To confirm that lung cancer needs aromatase, the team first searched for the enzyme in laboratory-grown lung cancer cells.
After finding it there, they also searched 53 non-small cell lung tumor samples from patients.
Using an antibody specific for aromatase and immunohistochemistry techniques, they found that 88 percent of the specimens from women and 86 percent from men contained high levels of the enzyme.

" Then we started getting excited," said Weinberg. The team proceeded to highlight actual aromatase activity with a radioactive tracer, finding the enzyme active in both the laboratory cells and the frozen specimens. They double-checked by depleting the cells of estrogen, then feeding them testosterone: If aromatase was at work, the cells would produce estrogen. They did.

" Once we saw that aromatase was active, we wanted to see if we could inhibit it with the same drugs they use for breast cancer," said Weinberg. The team treated their cells with the drug Anastrozole ( Arimidex ) for 48 hours, finding that it did in fact shut down aromatase activity and retard tumor growth in the lab.

" We found that tumors with both high and low levels of aromatase were sensitive to the drug," said Pietras.

Finally, the team grafted human lung tumors onto mice. One group of mice received Anastrozole for 21 days, while a second group did not. The tumors in the mice taking the drug grew 90 percent slower than the tumors in the untreated mice.